As a data integration technique, systems described in Patent Document 1 and Non-Patent Document 1 are known.
First, as shown in FIG. 15, a digraph unifying device described in Patent Document 1 includes an expressing means 13, a merging means 14, and a tag checking means 15. The digraph unifying device with such a configuration integrates digraphs in the following manner.
First, the expressing means 13 expresses an inputted digraph as a list of pairs composed of tags and partial digraphs corresponding thereto. This list is referred to as a tag list. Next, the merging means 14 merges tag lists corresponding to two digraphs.
Next, the tag checking means 15 checks whether partial digraphs corresponding to tags having the same name in the merged tag list are identical or not.
Further, in a graph integration algorithm described in Non-Patent Document 1, by using a rule for judgment of an identical node between two graphs, which is externally defined as a map function, integration is performed while consistency between the graphs is judged by the following algorithm.                Map M maps a blank node to a blank node.        With respect to all specific values (RDF literal) lit as nodes of Graph G, M(lit)=lit.        With respect to all intermediate nodes (RDF URI reference) uri as nodes of G, M(uri)=uri.        In a case that a triple (s, p, o) showing that a node and a node are connected by an edge is within G, a triple (M(s), p, M(o)) is within G′ always in this case.        
The graph integration process is performed based on consistency or inconsistency of each triple by the algorithm described above.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 5-204647
[Non-Patent Document 1] Graham Klyne et al., “RDF Concepts and Abstract Syntax,” W3C Recommendation, www.w3.org/TR/2004/REC-rdf-concepts-20040210/, (2004)
A problem regarding the abovementioned techniques is a tradeoff between an integration function and throughput. An existing integrating means realizes the process at [the number of nodes in a graph]2 by simplifying an integration function to be provided as in the method described in Patent Document 1.
On the other hand, as in the method described in Non-Patent Document 1, in a method for providing an advanced integration function of judging the identity of triples based on peripheral information of nodes and synonym information registered in a map, a processing time at a processing speed of ([the number of nodes in a graph]×[the average number of properties per node])2 is required. Therefore, the existing techniques have a problem that it is impossible to seek both an integration process and throughput.